Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high. Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions.

• Both A and R are true and R is correct explanation of A
• Both A and R are true but R is not correct explanation of A
• A is true but R is false
• A is false but R is true